1. Field of the Invention
This invention relates to a process of preparing an .alpha.-amylase inhibiting substance from a supernatant of an aqueous extract of wheat or wheat flour.
2. Description of the Prior Art
It is known that wheat or wheat flour contains a large quantity of .alpha.-amylase inhibiting substances. Such substances inhibit conversion of starch to saccharides even if sprouting of wheat ears occurs under such weather conditions as much rain in harvest season thereby preventing quality deterioration of the harvested wheat.
On one hand, .alpha.-amylase is an enzyme capable of at random hydrolyzing the .alpha.-1,4-glycoside bond of starch, glycogen and the like, which is extensively distributed in animals, plants, molds, bacteria, etc. In humans, there are .alpha.-amylase of saliva origin and .alpha.-amylase of pancreas origin, which play a role in converting starch to saccharides respectively in the mouth and the digestive tracts. Because the .alpha.-amylase inhibiting substance inhibits an activity of .alpha.-amylase, it is useful as a dieting agent for the prevention of obesity, as therapeutic agents for hyperglycemia and diabetes, as prophylactic agent for dental caries and so on.
In these circumstances, many attempts have been made to produce an .alpha.-amylase inhibitor by extraction from various raw materials. There are known a method for the extraction from betel nuts (Japanese Patent LOP Publn. No. 185995/1988) and a method for extracting an .alpha.-amylase inhibiting substance contained in wheat (Japanese Patent LOP Publn. No. 140727/1982).
The prior art processes of preparing .alpha.-amylase inhibiting substances from wheat or wheat flour include a very complicated operation which comprises a heat treatment of an aqueous extract of wheat or wheat flour, fractional precipitation of the resulting mass with an organic solvent, collecting a precipitated fraction, treating a solution fraction with an adsorbent, eluting an adsorbed substance with a salt solution and fractionating an eluate by chromatography. These processes are not efficient and economical for the production of .alpha.-amylase inhibiting substances.
In the manufacture of wheat gluten and wheat starch, a large amount of washing (waste liquid) has been produced from a step of eluting starch from dough or batter formed by kneading flour and water. A treatment of waste liquid needs much labor and cost. This treatment includes a troublesome problem in the industry. Since such waste liquid contains .alpha.-amylase inhibiting substances, recovery of the substances from the waste liquid would bring about combined effects of disposing the waste liquid and collecting valuable substances.